The invention relates to the unloading of the items, especially in pairs, on a sorting machine of the so-called "cross belt" type.
Such a machine, described for example in commonly owned European Patents EP-0 481 341. EP 0 518 180 and EP 0 556 866, arranges items on units constituted by trolleys capable of traveling along a path. Each trolley is fitted with a small rotating mat or belt which unloads the items to the side of the machine, whenever the unit reaches certain collecting systems assigned to each item.
In the machine described in the above patents the belts are of adequate length to accept at least two items set side-by-side, thus allowing, thanks to an appropriate handling process, to double the productivity of the existing machines.
In particular, this result is achieved by pre-positioning the two items arranged on the belt of the switching unit so as to allow their conveyance to their respective destinations by two successive starts of the belt.
To ensure a proper handling of this equipment it is therefore essential to load the items in pairs in a precise order consistent with the unloading order, and to achieve this without adversely affecting the loading time and without requiring complex procedures or some preliminary handling of the items.
It is also appropriate and essential that the items be loaded onto the machine closely parallel to the edges of the small mat of the sorting unit, so as to achieve a greater precision at the time of unloading.
It is in fact worth considering that these machines move forward at speeds of a few meters per second, and that in any machines fitted with numerous outlets, the latter are of a size hardly larger than that of the items to be sorted.
It is therefore necessary that the unloading operation, of a ballistic type, also occur with the utmost precision.
The most advanced existing machines comprise a series of loading stations constituted by a succession of rotating mats designed to load the items on the trolleys.
In particular, sorting machines are known in which the loading station mats are arranged at a 45.degree. angle with respect to the machine within a horizontal plane, so that the loading of the items can be carried out at a speed involving a component, in the direction of the forward motion of the trolleys, equal to the speed of the latter.
It is then possible, by appropriately starting the trolley mat at the loading instant, to feed the item onto the machine at an essentially zero relative speed in the direction of the forward motion, except for some later dampening of the push imparted to the item, by suitably slowing down the mat.
All this can provide an idea of the complexity of the handling systems of these machines.
It would be desirable to provide for the automatic loading of multiple items onto a unit of a cross-belt sorting machine, in a manner which allows the items to be arranged in the order of their unloading and to be fed onto the machine while observing the proper relative positioning and the expected alignment.